/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_fir_lattice_q15.c
 * Description:  Q15 FIR lattice filter processing function
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
  @ingroup groupFilters
 */

/**
  @addtogroup FIR_Lattice
  @{
 */

/**
  @brief         Processing function for Q15 FIR lattice filter.
  @param[in]     S          points to an instance of the Q15 FIR lattice structure
  @param[in]     pSrc       points to the block of input data
  @param[out]    pDst       points to the block of output data
  @param[in]     blockSize  number of samples to process
  @return        none
 */

void arm_fir_lattice_q15(
	const arm_fir_lattice_instance_q15 *S,
	const q15_t *pSrc,
	q15_t *pDst,
	uint32_t blockSize)
{
	q15_t *pState = S->pState;                     /* State pointer */
	const q15_t *pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q15_t *px;                                     /* Temporary state pointer */
	const q15_t *pk;                                     /* Temporary coefficient pointer */
	uint32_t numStages = S->numStages;             /* Number of stages in the filter */
	uint32_t blkCnt, stageCnt;                     /* Loop counters */
	q31_t fcurr0, fnext0, gnext0, gcurr0;          /* Temporary variables */

#if (1)
//#if !defined(ARM_MATH_CM0_FAMILY)

#if defined (ARM_MATH_LOOPUNROLL)
	q31_t fcurr1, fnext1, gnext1;                  /* Temporary variables for second sample in loop unrolling */
	q31_t fcurr2, fnext2, gnext2;                  /* Temporary variables for third sample in loop unrolling */
	q31_t fcurr3, fnext3, gnext3;                  /* Temporary variables for fourth sample in loop unrolling */
#endif

	gcurr0 = 0;

#if defined (ARM_MATH_LOOPUNROLL)

	/* Loop unrolling: Compute 4 outputs at a time */
	blkCnt = blockSize >> 2U;

	while (blkCnt > 0U) {
		/* Read two samples from input buffer */
		/* f0(n) = x(n) */
		fcurr0 = *pSrc++;
		fcurr1 = *pSrc++;

		/* Initialize state pointer */
		px = pState;

		/* Initialize coeff pointer */
		pk = pCoeffs;

		/* Read g0(n-1) from state buffer */
		gcurr0 = *px;

		/* Process first sample for first tap */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fcurr0;
		fnext0 = __SSAT(fnext0, 16);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext0 = (q31_t)((fcurr0 * (*pk)) >> 15U) + gcurr0;
		gnext0 = __SSAT(gnext0, 16);

		/* Process second sample for first tap */
		fnext1 = (q31_t)((fcurr0 * (*pk)) >> 15U) + fcurr1;
		fnext1 = __SSAT(fnext1, 16);
		gnext1 = (q31_t)((fcurr1 * (*pk)) >> 15U) + fcurr0;
		gnext1 = __SSAT(gnext1, 16);

		/* Read next two samples from input buffer */
		/* f0(n+2) = x(n+2) */
		fcurr2 = *pSrc++;
		fcurr3 = *pSrc++;

		/* Process third sample for first tap */
		fnext2 = (q31_t)((fcurr1 * (*pk)) >> 15U) + fcurr2;
		fnext2 = __SSAT(fnext2, 16);
		gnext2 = (q31_t)((fcurr2 * (*pk)) >> 15U) + fcurr1;
		gnext2 = __SSAT(gnext2, 16);

		/* Process fourth sample for first tap */
		fnext3 = (q31_t)((fcurr2 * (*pk)) >> 15U) + fcurr3;
		fnext3 = __SSAT(fnext3, 16);
		gnext3 = (q31_t)((fcurr3 * (*pk++)) >> 15U) + fcurr2;
		gnext3 = __SSAT(gnext3, 16);

		/* Copy only last input sample into the state buffer
		   which will be used for next samples processing */
		*px++ = (q15_t) fcurr3;

		/* Update of f values for next coefficient set processing */
		fcurr0 = fnext0;
		fcurr1 = fnext1;
		fcurr2 = fnext2;
		fcurr3 = fnext3;

		/* Loop unrolling.  Process 4 taps at a time . */
		stageCnt = (numStages - 1U) >> 2U;

		/* Loop over the number of taps.  Unroll by a factor of 4.
		   Repeat until we've computed numStages-3 coefficients. */

		/* Process 2nd, 3rd, 4th and 5th taps ... here */
		while (stageCnt > 0U) {
			/* Read g1(n-1), g3(n-1) .... from state */
			gcurr0 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext3;

			/* Process first sample for 2nd, 6th .. tap */
			/* Sample processing for K2, K6.... */
			/* f1(n) = f0(n) +  K1 * g0(n-1) */
			fnext0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fcurr0;
			fnext0 = __SSAT(fnext0, 16);

			/* Process second sample for 2nd, 6th .. tap */
			/* for sample 2 processing */
			fnext1 = (q31_t)((gnext0 * (*pk)) >> 15U) + fcurr1;
			fnext1 = __SSAT(fnext1, 16);

			/* Process third sample for 2nd, 6th .. tap */
			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15U) + fcurr2;
			fnext2 = __SSAT(fnext2, 16);

			/* Process fourth sample for 2nd, 6th .. tap */
			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15U) + fcurr3;
			fnext3 = __SSAT(fnext3, 16);

			/* g1(n) = f0(n) * K1  +  g0(n-1) */
			/* Calculation of state values for next stage */
			gnext3 = (q31_t)((fcurr3 * (*pk)) >> 15U) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fcurr2 * (*pk)) >> 15U) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fcurr1 * (*pk)) >> 15U) + gnext0;
			gnext1 = __SSAT(gnext1, 16);

			gnext0 = (q31_t)((fcurr0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);


			/* Read g2(n-1), g4(n-1) .... from state */
			gcurr0 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext3;

			/* Sample processing for K3, K7.... */
			/* Process first sample for 3rd, 7th .. tap */
			/* f3(n) = f2(n) +  K3 * g2(n-1) */
			fcurr0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fnext0;
			fcurr0 = __SSAT(fcurr0, 16);

			/* Process second sample for 3rd, 7th .. tap */
			fcurr1 = (q31_t)((gnext0 * (*pk)) >> 15U) + fnext1;
			fcurr1 = __SSAT(fcurr1, 16);

			/* Process third sample for 3rd, 7th .. tap */
			fcurr2 = (q31_t)((gnext1 * (*pk)) >> 15U) + fnext2;
			fcurr2 = __SSAT(fcurr2, 16);

			/* Process fourth sample for 3rd, 7th .. tap */
			fcurr3 = (q31_t)((gnext2 * (*pk)) >> 15U) + fnext3;
			fcurr3 = __SSAT(fcurr3, 16);

			/* Calculation of state values for next stage */
			/* g3(n) = f2(n) * K3  +  g2(n-1) */
			gnext3 = (q31_t)((fnext3 * (*pk)) >> 15U) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fnext2 * (*pk)) >> 15U) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fnext1 * (*pk)) >> 15U) + gnext0;
			gnext1 = __SSAT(gnext1, 16);

			gnext0 = (q31_t)((fnext0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			/* Read g1(n-1), g3(n-1) .... from state */
			gcurr0 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext3;

			/* Sample processing for K4, K8.... */
			/* Process first sample for 4th, 8th .. tap */
			/* f4(n) = f3(n) +  K4 * g3(n-1) */
			fnext0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fcurr0;
			fnext0 = __SSAT(fnext0, 16);

			/* Process second sample for 4th, 8th .. tap */
			/* for sample 2 processing */
			fnext1 = (q31_t)((gnext0 * (*pk)) >> 15U) + fcurr1;
			fnext1 = __SSAT(fnext1, 16);

			/* Process third sample for 4th, 8th .. tap */
			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15U) + fcurr2;
			fnext2 = __SSAT(fnext2, 16);

			/* Process fourth sample for 4th, 8th .. tap */
			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15U) + fcurr3;
			fnext3 = __SSAT(fnext3, 16);

			/* g4(n) = f3(n) * K4  +  g3(n-1) */
			/* Calculation of state values for next stage */
			gnext3 = (q31_t)((fcurr3 * (*pk)) >> 15U) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fcurr2 * (*pk)) >> 15U) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fcurr1 * (*pk)) >> 15U) + gnext0;
			gnext1 = __SSAT(gnext1, 16);

			gnext0 = (q31_t)((fcurr0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			/* Read g2(n-1), g4(n-1) .... from state */
			gcurr0 = *px;

			/* save g4(n) in state buffer */
			*px++ = (q15_t) gnext3;

			/* Sample processing for K5, K9.... */
			/* Process first sample for 5th, 9th .. tap */
			/* f5(n) = f4(n) +  K5 * g4(n-1) */
			fcurr0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fnext0;
			fcurr0 = __SSAT(fcurr0, 16);

			/* Process second sample for 5th, 9th .. tap */
			fcurr1 = (q31_t)((gnext0 * (*pk)) >> 15U) + fnext1;
			fcurr1 = __SSAT(fcurr1, 16);

			/* Process third sample for 5th, 9th .. tap */
			fcurr2 = (q31_t)((gnext1 * (*pk)) >> 15U) + fnext2;
			fcurr2 = __SSAT(fcurr2, 16);

			/* Process fourth sample for 5th, 9th .. tap */
			fcurr3 = (q31_t)((gnext2 * (*pk)) >> 15U) + fnext3;
			fcurr3 = __SSAT(fcurr3, 16);

			/* Calculation of state values for next stage */
			/* g5(n) = f4(n) * K5  +  g4(n-1) */
			gnext3 = (q31_t)((fnext3 * (*pk)) >> 15U) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fnext2 * (*pk)) >> 15U) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fnext1 * (*pk)) >> 15U) + gnext0;
			gnext1 = __SSAT(gnext1, 16);

			gnext0 = (q31_t)((fnext0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			stageCnt--;
		}

		/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
		stageCnt = (numStages - 1U) % 0x4U;

		while (stageCnt > 0U) {
			gcurr0 = *px;

			/* save g value in state buffer */
			*px++ = (q15_t) gnext3;

			/* Process four samples for last three taps here */
			fnext0 = (q31_t)((gcurr0 * (*pk)) >> 15U) + fcurr0;
			fnext0 = __SSAT(fnext0, 16);

			fnext1 = (q31_t)((gnext0 * (*pk)) >> 15U) + fcurr1;
			fnext1 = __SSAT(fnext1, 16);

			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15U) + fcurr2;
			fnext2 = __SSAT(fnext2, 16);

			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15U) + fcurr3;
			fnext3 = __SSAT(fnext3, 16);

			/* g1(n) = f0(n) * K1  +  g0(n-1) */
			gnext3 = (q31_t)((fcurr3 * (*pk)) >> 15U) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fcurr2 * (*pk)) >> 15U) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fcurr1 * (*pk)) >> 15U) + gnext0;
			gnext1 = __SSAT(gnext1, 16);

			gnext0 = (q31_t)((fcurr0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			/* Update of f values for next coefficient set processing */
			fcurr0 = fnext0;
			fcurr1 = fnext1;
			fcurr2 = fnext2;
			fcurr3 = fnext3;

			stageCnt--;
		}

		/* The results in the 4 accumulators, store in the destination buffer. */
		/* y(n) = fN(n) */

#ifndef  ARM_MATH_BIG_ENDIAN
		write_q15x2_ia(&pDst, __PKHBT(fcurr0, fcurr1, 16));
		write_q15x2_ia(&pDst, __PKHBT(fcurr2, fcurr3, 16));
#else
		write_q15x2_ia(&pDst, __PKHBT(fcurr1, fcurr0, 16));
		write_q15x2_ia(&pDst, __PKHBT(fcurr3, fcurr2, 16));
#endif /* #ifndef  ARM_MATH_BIG_ENDIAN */

		blkCnt--;
	}

	/* Loop unrolling: Compute remaining outputs */
	blkCnt = blockSize % 0x4U;

#else

	/* Initialize blkCnt with number of samples */
	blkCnt = blockSize;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

	while (blkCnt > 0U) {
		/* f0(n) = x(n) */
		fcurr0 = *pSrc++;

		/* Initialize state pointer */
		px = pState;

		/* Initialize coeff pointer */
		pk = pCoeffs;

		/* read g2(n) from state buffer */
		gcurr0 = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext0 = (((q31_t) gcurr0 * (*pk)) >> 15U) + fcurr0;
		fnext0 = __SSAT(fnext0, 16);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext0 = (((q31_t) fcurr0 * (*pk++)) >> 15U) + gcurr0;
		gnext0 = __SSAT(gnext0, 16);

		/* save g1(n) in state buffer */
		*px++ = (q15_t) fcurr0;

		/* f1(n) is saved in fcurr0 for next stage processing */
		fcurr0 = fnext0;

		stageCnt = (numStages - 1U);

		/* stage loop */
		while (stageCnt > 0U) {
			/* read g2(n) from state buffer */
			gcurr0 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext0;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext0 = (((q31_t) gcurr0 * (*pk)) >> 15U) + fcurr0;
			fnext0 = __SSAT(fnext0, 16);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext0 = (((q31_t) fcurr0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			/* f1(n) is saved in fcurr0 for next stage processing */
			fcurr0 = fnext0;

			stageCnt--;
		}

		/* y(n) = fN(n) */
		*pDst++ = __SSAT(fcurr0, 16);

		blkCnt--;
	}

#else
	/* alternate version for CM0_FAMILY */

	blkCnt = blockSize;

	while (blkCnt > 0U) {
		/* f0(n) = x(n) */
		fcurr0 = *pSrc++;

		/* Initialize state pointer */
		px = pState;

		/* Initialize coeff pointer */
		pk = pCoeffs;

		/* read g0(n-1) from state buffer */
		gcurr0 = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext0 = ((gcurr0 * (*pk)) >> 15U) + fcurr0;
		fnext0 = __SSAT(fnext, 16);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext0 = ((fcurr0 * (*pk++)) >> 15U) + gcurr0;
		gnext0 = __SSAT(gnext0, 16);

		/* save f0(n) in state buffer */
		*px++ = (q15_t) fcurr0;

		/* f1(n) is saved in fcurr for next stage processing */
		fcurr0 = fnext0;

		stageCnt = (numStages - 1U);

		/* stage loop */
		while (stageCnt > 0U) {
			/* read g1(n-1) from state buffer */
			gcurr0 = *px;

			/* save g0(n-1) in state buffer */
			*px++ = (q15_t) gnext0;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext0 = ((gcurr0 * (*pk)) >> 15U) + fcurr0;
			fnext0 = __SSAT(fnext0, 16);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext0 = ((fcurr0 * (*pk++)) >> 15U) + gcurr0;
			gnext0 = __SSAT(gnext0, 16);

			/* f1(n) is saved in fcurr0 for next stage processing */
			fcurr0 = fnext0;

			stageCnt--;
		}

		/* y(n) = fN(n) */
		*pDst++ = __SSAT(fcurr0, 16);

		blkCnt--;
	}

#endif /* #if !defined(ARM_MATH_CM0_FAMILY) */

}

/**
  @} end of FIR_Lattice group
 */
